1. CSC/CRE Technical Review 6 October 2008

2. 2 Outline  Review the process used in calculating Power Transfer Distribution Factors (PTDFs).  Information posted at: http://www.ercot.com/calendar/2008/10/20081008-TACWMS http://www.ercot.com/calendar/2008/10/20081008-TACWMS  CRE recommendations distributed on October 3 rd.

3. 3 6 October 2008 PTDF vs. GSF  Power Transfer Distribution Factors (PTDFs) represent the percent of power transfer that flows on a transmission facility. PTDFs are used to estimate the change in flows that occur from a particular transfer and identifying which elements are impacted by the transfer.  Generator Shift Factors (GSFs) represent the change in flow on an element as a result of increasing generation at a node. GSFs are more useful in identifying the generator pairs that can impact a specific element.  Both PTDF and GSFs can be calculated using similar assumptions.  Source: http://www.pserc.org/cgi-pserc/getbig/publicatio/2001public/tcc_tutorialjuly01.pdfhttp://www.pserc.org/cgi-pserc/getbig/publicatio/2001public/tcc_tutorialjuly01.pdf

4. 4 6 October 2008 PTDF process For each of the CSC Scenarios 3b, 3i, and 3h -  ERCOT coordinated Market Participant resources to assist in the calculation of PTDFs for each scenario  PowerWorld and Excel were used as the tools to calculate PTDFs for base case and contingencies of CSCs and CREs.  For the Base Case and each pair of contingency-monitored elements, the 3 plants with highest of GSFs for both directions were identified to review whether local solutions were feasible.

5. 5 6 October 2008 PTDF Calculation Assumptions  Oklaunion movable and located in the West zone under Scenario 3i and 3b but not movable and located in the North zone under Scenario 3h.  Pmax available to resolve constraint for all unit movable units in each zone

6. 6 6 October 2008 ERCOT’s CRE recommendations  ERCOT based it’s CRE recommendations on the results generated by the test outlined in Protocols Section 7.2.3  ERCOT is also permitted by the Protocols to select CREs that can provide improved operational control.  In determining whether a CRE provides improved operational control ERCOT reviewed the PTDF results and the location of the CRE.

7. 7 6 October 2008 Who’s on first? 1)This column states whether the CRE was a 2008 CRE. 2)Explains the criteria used for recommending the line as a CRE; if a CRE only passed for a specific scenario, the scenario is provided in parenthesis. 3)Denotes which CSC scenario a particular CRE is recommended for; “x” marks the spot. 1 2 3

8. 8 6 October 2008 Average Weighted Shift Factor Scenario 3b AWSF Table ZoneW-NS-NN-SN-HN-W North0.0082780.01443-0.014430.008156-0.00828 South0.023950.384565-0.38456-0.22998-0.02395 West0.3751490.024752-0.02475-0.02098-0.37515 Houston0.0139440.244188-0.24419-0.33006-0.01394 Scenario 3h & i AWSF Table ZoneW-NS-NN-SN-HN-W North0.0060290.014347-0.014350.007204-0.00603 South0.0296190.384565-0.38456-0.22998-0.02962 West0.383520.028084-0.02808-0.02294-0.38352 Houston0.0184890.244188-0.24419-0.33006-0.01849

9. 9 6 October 2008 Questions